Golfers have long recognized that they could alter the weight, balance, and performance characteristics by selectively adding weight to club heads. Typically, weight is added by applying thin strips of lead tape with an adhesive backing to the club head. In this manner the swing weight is increased and the center of gravity (CG) is altered to change the dynamics of the head during the swing and, therefore, the ball flight characteristics after contact. The location of the lead tape, however, is generally limited to the back, crown, and sole of the club heads, where it would best stay affixed and not alter the look of the club. However, this limits the adjustability options available to the golfer. For example, the lead tape can not be put on the face of the club to move the CG closer to the front of the club. Forward movement of the center of gravity is more desirable to some golfers who want the club to be easier to “work”, that is, to shape shots both in a left-to-right manner and in a right-to-left manner.
Furthermore, use of lead tape is generally an additive process, increasing the swing weight and total weight of the club was increased and oftentimes negatively affecting other performance characteristics of the club. Some golfers attempt to overcome this obstacle by grinding down or using other means to reduce the weight of the club. However, this often damages the protective finish of the club or the shape and configuration intended by the club designer, negatively affects the after market value of the club, and is both difficult and time-consuming for the golfer to adjust.
Furthermore, manufacturers of golf clubs have encountered problems manufacturing individual clubs to identical specifications, because of variances of the individual components themselves and when assembled together. Generally, manufacturers build clubs to a weight at, or slightly below, a targeted weight specification and then add additional weight to either or both of the head and the shaft, as desired, to increase either or both of the total weight and the swing weight to the desired specification. Additional weight is commonly added by pouring lead powder into the bottom of the shaft and sealing the shaft with a cork or other means. Alternatively, lead powder is mixed with putty, epoxy, or other materials that are inserted into the end of the shaft of the assembled head and shaft to facilitate this final weight adjustment by the manufacturer. These methods, however, may alter the CG of the club away from the optimal location, adversely effecting performance and feel.
Additionally, a common practice is to inject a hot melt glue or similar material into a hole in the club head during final assembly to arrive at a prescribed swing weight. The location that the glue puddles and adheres to the inner walls is determined by the orientation of the head while the glue is still hot and fluid. This technique is also used to customize the center of gravity of the club head for specific golfers' needs. The location of the glue, however, is generally limited to one broad area due to the closed process, and once the glue is set, the glue is not adjustable.
Therefore, there is a need for a golf club head with a customizable CG that allows the CG to be altered by either or both the golfer and the manufacturer, both prior to and following final manufacture.